Building framing beams or studs composed of a cementitious material and method of making

ABSTRACT

A cementitious material beam for use in the building construction industry and a method of fabricating such beam.

FIELD OF THE INVENTION

This invention relates to a building construction product which incorporates cementitious materials and more particularly, to a framing beam or stud formed from cementitious and other materials and the method of fabricating such product.

BACKGROUND OF THE INVENTION

Although the number of residential buildings in the United States ebbs and flows, for the preceding decade between 1.5 and 2 million conventional, single-family homes have been built each year. A typical building home uses 15,000 board feet of lumber. Nearly 40% of lumber used in the residential home building industry is imported, primarily from Canada. Thus, the amount of lumber that is used in the home building industry is highly significant, affects the U.S. trade balance and most importantly has a significant impact on global ecology.

Problems with global warming indicate that the potential cause of such climatic change has been forest depletion resulting in lessening of CO₂ fixation. In addition to other ecological problems resulting in the high use of lumber, the decreasing supply of large diameter trees has made the cost of standard dimensional lumber increase resulting in higher building costs of new residential homes.

In the construction of a residential building having a current cost of approximately $200,000, 20% of the cost is in framing and trusses. Thus, studs, typically 2×4 and 2×6 dimensional lumber, represent a significant cost proportion of the overall building and consumes a substantial amount of lumber. Nevertheless, dimensional lumber framing studs are used extensively in residential buildings and steel studs have only been successfully used in commercial buildings. Steel framing studs have been unable to penetrate the residential building products market.

In addition to the simple fact that framing studs utilize substantial lumber there are various problems with standard dimension lumber studs. For example, it is estimated that as much as 35% of the total board feet used in framing a building will end up in waste. In part, this is due to the fact that younger timber has been used more recently in framing applications and it is less stable, has poor dimensional stability, and has poor tensile strength. Moreover, these studs can bow, warp, shrink and twist making them unsuitable or marginally suitable for use in framing a house. In addition, the standard dimensional studs may have cracks, develop splits, or have knots in areas of the stud that will result in waste.

The term stud is used in the industry primarily to designate the vertical structural components, that in cooperation with sheathing, are used to build walls. The term “beam” is used in this patent to refer to any elongated structural member used in a variety of building construction applications.

Some of these problems have been addressed by the use of what is referred to in the industry as “engineered wood” using various types of lamination or strands to create a synthetic wooden beam that allows the use of fast growth trees and recycled materials. However, currently a standard dimensional #2 pine beam suitable for a stud costs approximately $1.00 per board foot, whereas engineered wood may cost on the order of $1.25-$2.00 per board. It is also true that metal studs are typically more expensive than either type of wooden beam.

In addition to these ecological and cost issues, it is also true that wood products are subject to termite infestation, rotting, mildew, and poor resistance to fire. Even if metal studs were cost competitive, they do not have the thermal and noise insulation characteristics of wooden studs, present problems with respect to the installation of pipes and electrical conduit within the building walls, and involve different methods and construction skills that are less available than the standard techniques of creating a residential house frame with manual or powered nails for joining studs in place.

In the current residential building industry, there has been a trend toward houses that have walls constructed of concrete utilizing insulating concrete forms that remain in place to provide thermal and noise suppression. The industry has also adopted many types of cementitious materials for exterior finishing of walls either by the use of stucco or similar materials, or by manufactured siding also using cementitious fiber-strengthened shingles or slats. However, there does not appear to be any widespread use in the residential homebuilding industry in the United States of cementitious products that are used as framing components, that is, a replacement for the ubiquitous 2×4 and 2×6 lumber beams.

Accordingly, there is a current need in the residential homebuilding industry for beams or studs that are made of cementitious material so as to relieve some or all of the problems identified above.

SUMMARY OF THE INVENTION

This invention provides a beam fabricated primarily of cementitious materials that may be used, for example, as framing studs in wall systems. The beam is constructed from an elongated, rectangular, tubular hollow member, a screen or mesh material encasing the tubular member, a plurality of rectangular plates having a central opening and at least four circular openings adjacent corners of the plates, the plates disposed within the tubular member at longitudinally spaced locations, elongated steel rods threaded through the plate circular openings and extending along the full length of the cardboard tubular member, and a cementitious mixture filling the tubular member comprising cement, sand, water and a low density expanded silicon dioxide material.

The invention further includes a method for building the above-described beam comprising the steps of providing an elongated rectangular, tubular member, wrapping a screen or mesh material around the tubular member and securing it thereto, providing a plurality of rectangular plates having perimeter dimensions slightly less than the inner dimensions of a cross section of the rectangular tubular member wherein each of the plates has a central opening and a plurality of circular openings near the corners of the rectangular plate, providing steel rods that are inserted through the openings in the rectangular plates, securing the plates at spaced apart locations along the rods, inserting the rod-plate subassembly into the rectangular tubular member, filling the tubular member with a cementitious mixture that includes at least cement, sand, water and a low density, expanded silicon dioxide material, and allowing the cementitious mixture to set whereby a high strength relatively rigid beam is formed.

DRAWINGS

The accompanying drawing illustrates the preferred embodiment of the invention as well as other information pertinent to the disclosure of the method and article, in which:

FIG. 1 is a perspective view of a preferred embodiment of a cementitious beam;

FIG. 2 is a front elevational view of a plate; and

FIG. 3 is a cross-sectional view of the completed stud shown in FIG. 1.

DETAILED DESCRIPTION OF ONE EMBODIMENT OF THE INVENTION

Referring now to FIG. 1, there is shown a beam comprising an embodiment of the invention. The beam 10 when used as a wall stud may be of variable length such as 8-10 feet depending upon the architecturally specified wall height of, for example, a residential building wall. The beam 10 has a generally rectangular cross-sectional shape which may be the same or approximately equal to standard dimensional lumber sizes used for framing such as a 2×4 or 2×6.

Referring now to FIG. 3, there is shown a cross section of the beam 10 as shown in FIG. 1. This embodiment includes an elongated, rectangular, tubular cardboard or plastic member 12. The cardboard may be approximately ⅛ inch thick and may be comprised of multiple layers of thin cardboard material as is well known in the art. The inner surface of the tubular member 12 may have a coating that is relatively impervious to water so that the cardboard does not absorb the water in the cementitious mixture as will be later explained. A material in the nature of a screen or mesh synthetic fabric or flexible metallic material 13 is wrapped around the exterior of the tubular cardboard member and secured thereto by means of a glue or ordinary staples.

As seen best in FIG. 2, there is provided a plurality of rectangular relatively rigid plates 14 having a central opening 16 and at least four circular openings 18 adjacent the corners of the rectangular plate 14. The opening 16 may be of any configuration; its size is preferably large enough so that the cementitious mixture that will be poured into the tubular cardboard member 12 as later explained will allow the material to freely flow. The plates 14 are spaced at least six inches, and preferably 12 inches, but most preferably nine inches apart at longitudinally-spaced locations. Each of the plates 14 have a rectangular perimeter that is roughly equal to the inner perimeter of the cardboard tubular member 12. The rectangular plates may be made from a plastic material or a very thin metal which is more or less rigid. It will be understood that the material is not critical to the embodiment shown so long as it is compatible with the cementitious mixture. Nor is the number or position of circular openings in the plate critical so long as the two rods, to be described, are positioned near the tubular member inner surface and away from the center region of the vertical edges where nails will be driven.

The embodiment of the beam also includes high tensile strength rods or wires 20, at least one for each plate corner opening. In the embodiment shown, the rods are 5/32 inch in diameter steel but may be less, such as ⅛ inch in diameter, or larger such as 3/16 in diameter. The specific diameter is not critical to the invention it being understood that the rods provide tensile and high bending strength to the completed beam. The plates 14 serve to position the rods within the tubular cardboard member during fabrication. The plates are secured to the rods at spaced apart locations.

A cementitious mixture shown at 22 in FIG. 3 fills the cardboard tubular member 12. This cementitious mixture includes cement, such as Portland cement, in an approximate percentage by weight of 10%. The mixture further includes an exterior stucco mixture such as Western 1-KOTE Exterior Stucco product available from Western Stucco Products Co., Inc. located in Glendale, Ariz. which comprises a stucco material reinforced with chopped fibers. This stucco material may be approximately 15% of the cementitious mixture 22 by weight. The cementitious mixture 22 also includes sand that is preferably clean and free from deleterious amounts of loam, clay, silk, soluble salts, and organic matter. The sand must comply with ASTM standard C 144 and must be graded in accordance with selected standard sieve sizes.

The cementitious mixture 22 also includes a low-density expanded silicon dioxide material such as but not limited to Perlite. Perlite is a primarily silicon dioxide natural material that can be heated into an expanded low density state. Typical expanded Perlite has a bulk density of between 30-150 kg/m³. In its natural state, Perlite is an amorphous volcanic glass with a high water content such that when heated causes the entrapped water to escape and vaporize leading to an expansion of the material from 7-16 times its original volume. Perlite is relatively low cost and is used in a variety of applications including, within the construction field, in plasters, mortars, insulation, ceiling tiles and filter aids. Perlite may also be used in iron foundries, as cryogenic insulation, and as a lightweight aggregate in a cementitious material that contributes fire resistance. A typical analysis of Perlite may comprise: 70-75% silicon dioxide; 12-15% aluminum oxide; 3-4% sodium oxide; 3-5% potassium oxide; 0.5-2% iron oxide; 0.2-0.7% magnesium oxide; 0.2-0.7% magnesium oxide; 0.5-1.5% calcium oxide; and 3-5% loss on ignition. There are various substitutes for Perlite that may be suitable for this application including Vermiculite, also in an expanded state. Vermiculite may also be used as an aggregate in place of sand and/or gravel. For the present invention, Perlite is preferred. Where Perlite is used, it is typically 15% of the overall weight of the cementitious mixture.

A cementitious mixture may also include porcelain set mortar, a type of adhesive, in the amount of approximately 5%.

A beam in accordance with the embodiment of this invention is made by taking the elongated rectangular, tubular, cardboard member and wrapping a screen material having a relatively fine mesh around the cardboard member and securing it thereto. The elongated wire or rods are threaded through the corner openings in the plates 14 and the plates are secured along the length of the rod by crimping or similar deformation of the rod material to maintain the plate 14 in spaced apart location as described above. This subassembly comprising the rods and plates is then inserted into the tubular rectangular member. The tubular member may then be stood on end or oriented at an angle to the surface on which the fabrication is being performed. The cementitious mixture in accordance with the formula as set forth above is in a semi-liquid or slurry form and is poured into the tubular member so as to completely encase the rods and steel plates in place. Although not required, it is desirable to apply a cementitious mixture 24 to the exterior surface of the cardboard member which in the semi-liquid or pourable state will allow the mesh or screen 13 to become embedded within the cementitious mixture 24. Since the cementitious mixture 24 on the exterior of the cardboard member is relatively thin, on the order of ⅛ inch thick, it dries fairly rapidly compared to the drying of the cementitious mixture 22 within the cardboard member. It has been found desirable to let the assembly set for 30 days to become fully set or cured and ready for use in building construction applications.

One alternative method for fabrication is to prestress the steel rods 20 prior to application of the cementitious mixture 22 and to maintain the tensile load on the rods until the cementitious mixture sets at which time the load is released causing the steel rod to contract and thus create a compression load on the cementitious mixture which will aid in the bending strength of the finished product.

The above-described embodiment of the invention will be understood by those having ordinary skill in the art as suggesting a particular type of, for example, cementitious mixture but various constituents may be altered in the cementitious mixture and still attain the objectives of the invention. Furthermore, the rods may be of steel or other high tensile strength metal or even synthetic materials formed from plastic, fiber-plastic, or even nanotube materials. As indicated above, the rectangular plates may be either metal or a synthetic plastic material or cardboard, or even wood that is relatively rigid and will serve to maintain the rods in place in the corners of the finished beam. The screen mesh may be of various sizes and has the purpose of providing strength to the finished beam when the screen or mesh material has been set in the thin layer of cementitious mixture on the exterior surface of the tubular member. It will therefore be appreciated that although the embodiment was described with a certain degree of particularity, it is to be understood that the disclosure has been made by way of example only and that the present invention is not limited to the features of the embodiment described and illustrated herein but includes all variations and modifications within the scope and spirit of the invention as hereinafter claimed. 

1. A cementitious material building construction beam comprising: an elongated, rectangular, tubular hollow member; a screen material encasing the tubular member; a plurality of rectangular, relatively rigid plates having a central opening and at least four circular openings adjacent the corners of said plates, said plates disposed within said tubular member at longitudinally spaced apart locations; high tensile strength rods, at least one for each plate corner opening, extending through the plate corner openings along the full length of the tubular member; a cementitious mixture filling the tubular member, comprising cement, sand, water and a low density, expanded silicon dioxide material.
 2. The beam of claim 1 additionally including an exterior thin layer of cementitious mixture applied to the outside of the tubular member so as to embed screen material within the mixture.
 3. The beam of claim 2 wherein said cementitious mixture forming the exterior layer has the same composition as the mixture filling the tubular member.
 4. The beam of claim 3 wherein said layer is approximately 1/16 inch thick.
 5. The beam of claim 1 wherein the tubular member is cardboard.
 6. The beam of claim 5 wherein said rectangular plates are made of sheet metal.
 7. The beam of claim 6 wherein the dimensions of the rectangular, tubular cardboard member are approximately equal to the dimensions of a standard, dimensional two by four.
 8. The beam of claim 1 wherein said rod has a nominal diameter between ⅛ inch and 3/16 inch.
 9. The beam of claim 8 wherein said rod diameter is 5/32 inch.
 10. The beam of claim 1 wherein said cementitious mixture comprises prior to setting 30% water, 10% sand, 15% Perlite, 20% cement, 5% mortar, 10% cardboard and 10% miscellaneous.
 11. The beam of claim 10 wherein said cementitious mixture contains synthetic fibers.
 12. The beam of claim 11 wherein said tubular member has a thickness of about ⅛ inch.
 13. The beam of claim 1 wherein said cementitious material is permitted to set for 30 days prior to use of the beam.
 14. The beam of claim 1 wherein said rods are prestressed prior to embedding in said cementitious mixture and relieved after said mixture has set.
 15. A building construction beam of cementitious material comprising: an elongated, rectangular, tubular hollow member; a plurality of rectangular plates having a central opening and at least two circular openings adjacent to the corners of said plates, said plates disposed within said tubular member at longitudinally spaced apart locations; elongated high tensile strength wires, at least one for each plate corner opening, extending through the plate circular openings along the full length of the tubular member; and a cementitious mixture filling the tubular hollow member comprising cement, sand, water and a low density, expanded silicon dioxide material.
 16. The building construction beam of claim 15 wherein said expanded silicon dioxide material is Perlite.
 17. The building construction beam of claim 16 additionally including a screen material encasing the tubular hollow member.
 18. The building construction beam of claim 17 wherein said elongated, rectangular, tubular member is formed of cardboard.
 19. The building construction beam of claim 17 wherein said elongated, rectangular, tubular member is cardboard.
 20. A method for fabricating a cementitious material building construction beam comprising the steps of: providing an elongated, rectangular, tubular hollow member; wrapping a screen material so as to encase the tubular cardboard member; providing a plurality of rectangular plates having a central opening and at least two circular openings adjacent two of the corners of the plates; positioning the plurality of rectangular plates within the tubular cardboard member at spaced apart locations; inserting elongated high tensile strength rods through said circular plate openings thereby positioning the rods to be adjacent the tubular cardboard member; filling the tubular hollow member with a cementitious mixture including cement, sand, water and a low density, expanded silicon dioxide material.
 21. The method of claim 20 including applying an exterior thin layer of cementitious material to the outside of the tubular member so as to encase the screen material in a relatively thin layer of cementitious mixture.
 22. The method of claim 21 wherein the elongated rods are inserted into the circular openings of the plurality of plates and are secured in a spaced apart location prior to positioning the rod-plate subassembly into the rectangular tubular member.
 23. The method of claim 22 wherein the cementitious mixture comprises 30% water, 10% sand, 15% Perlite, 20% cement, 5% mortar, 10% cardboard and 10% miscellaneous.
 24. The method of claim 20 wherein the final step of the fabrication process is permitting the cementitious mixture to cure for a period of at least 30 days. 